There are many circuit designs that require a high frequency switch. An ideal switch has very low losses in the "on" mode while providing very high losses in the "off" mode. In both modes, the switch must provide a high degree of isolation in the reverse direction. In addition, the ideal switch has a flat gain over the operating frequency range of the switch and settles quickly after being switched. Finally, cost is always a factor in switch design. The ideal switch should have a low part count and have as few control lines as possible to prevent switch-to-switch crosstalk in circuits employing multiple switches.
Mechanical switches can provide many of these desirable features. However, such switches have slow switching times and are subject to wear. Accordingly, there are many applications in which mechanical switches cannot be used.
Switches based on PIN diodes in a biased divider configuration followed by a high input impedance amplifier have also been utilized. However, these switches have unsatisfactorily high losses in the "on" state and/or insufficient losses in the "off" state to provide the needed on/off switching ratio for many applications. In addition, these switches generate harmonic distortions. Finally, these switches have a high part count that makes them commercially unattractive for many applications.
Broadly, it is the object of the present invention to provide an improved high frequency switch.
It is a further object of the present invention to provide a high frequency switch that more nearly resembles the ideal switch discussed above than prior art switches.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.